Bypass filter assembly and method of obtaining a filtered sample

ABSTRACT

A bypass filter assembly and method of obtaining a filtered sample from a process stream or the like in which the process stream is introduced into a filter chamber so as to produce a symmetrical bifurcated flow pattern of fluid therein which promotes a counter-rotating scouring or cleaning action on the membrane filter in the chamber. The housing of the assembly is divided into two sections. The inlet and outlet ports for the process stream and the filtered sample port are all located in one section of the housing so that the other section, namely the filter cap, may be removed from the first section without disconnecting any flow lines from the cap, thus facilitating rapid removal of the cap and replacement of the filter element therein.

United States Patent Gomez et al.

[ July4, 1972 [72] Inventors: Ray J. Gomez, Arcadia; Kenneth B. Sawa,

Yorba Linda, both of Calif.

[73] Assignee: Beckman Instruments, Inc.

[22] Filed: Sept. 25, 1970 [211 App]. No.: 75,355

[52] US. Cl ..2l0/409, 210/433, 210/445 [51] Int. Cl. ..B01d 35/22, BOId31/00 [58] Field ofSearch ..210/23, 321,404, 433,445, 210/447, 450, 453,456

[56] References Cited UNITED STATES PATENTS 3,133,132 5/1964 Loeb et al..264/49 3,399,972 9/1968 Skeggs et al. ..2l0/32l X FILTERED SAMPLE TOANALYZER OTHER PUBLICATIONS Mahjikian et al., Improvement in FabricationTechniques for Reverse Osmosis Desalination Membranes," from Proceedingsof the First International Symposium on Water Desalination, pp. 159, and161-164 relied on Primary Examiner-Frank A. Spear, Jr. Attorney-ThomasL. Peterson and Robert J. Steinmeyer [5 7] ABSTRACT A bypass filterassembly and method of obtaining a filtered sample from a process streamor the like in which the process stream is introduced into a filterchamber so as to produce a symmetrical bifurcated flow pattern of fluidtherein which promotes a counter-rotating scouring or cleaning action onthe membrane filter in the chamber. The housing of the assembly isdivided into two sections. The inlet and outlet ports for the processstream and the filtered sample port are all located in one section ofthe housing so that the other section, namely the filter cap, may beremoved from the first section without disconnecting any flow lines fromthe cap, thus facilitating rapid removal of the cap and replacement ofthe filter element therein.

5 Claims, Drawing Figures PROCESS STREAM INLET PROCESS STREAM OUTLETPATENTEDJUL 4 I972 3.674.153

SHEET 10F 2 PROCESS STREAM FILTERED SAMPLE TO ANALYZER PROCESS STREAM 2OUTLET INVENTORS RAY J. GOMEZ KENNETH B. SAWA ATTORNEY Pmemmwr 4 m23574.153

SHEET 2 OF 2 INVENTORS FIG. 5 RAY J. GOMEZ KENNETH a. SAWA BY //M %%WATTORNEY BYPASS FILTER ASSEMBLY AND METHOD OF OBTAINING A FILTEREDSAMPLE BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates generally to filters and, more particularly, to abypass filter assembly and method of obtaining a filtered sample from aprocess stream or the like.

2. Description of the Prior Art A basic requirement of all analyticalinstrumentation is that the sample to be analyzed must be properlyconditioned prior to introduction thereof into the instrument. A primerequisite for sample conditioning systems is the removal of particulatematerial such as rust, iron sulfide, catalyst dust, etc., to preventplugging of sample lines and damage to the instrument.

Heretofore, bypass filters utilized in connection with analyticalinstrumentation have generally been of the low washing action type inthat the filter elements positioned therein were not subjected tosufficient turbulent washing action. As a result, the filter elementshad to be continually replaced because of clogging due to the particlescontained in the process stream, thus causing an excessive pressure dropin the flow system.

US. Pat. No. 3,459,307 to Collins discloses a bypass filter assembly inwhich the process stream is introduced tangentially into the cylindricalchamber of the assembly thereby creating a turbulent flow of the streamwithin the chamber for the purpose of providing a self-cleaning actionon the filter element therein. The purpose of the instant invention isto produce a different form of turbulent flow within a bypass filterassembly so as to achieve a self-cleaning action of the filter elementin the assembly which is at least as effective as, if not better than,that achieved in the aforementioned Collins filter assembly. Inaddition, the Collins bypass filter requires the removal of a sampleline from the filter cap in order to gain entrance to the interior ofthe assembly to replace the filter element therein. This requires asubstantial delay and inconvenience to the operator and, therefore, itis another purpose of the present invention to provide a filter assemblyin which it is not necessary to remove any lines from the filter capthereof.

SUMMARY OF THE INVENTION According to the principal aspect of thepresent invention, there is provided a bypass filter assembly and methodof obtaining a filtered sample from a process stream or the like inwhich the process stream is introduced into a filter chamber so as toproduce a symmetrical bifurcated flow pattern of fluid therein whichpromotes a counter rotating scouring or cleaning action on the membranefilter in the chamber. According to another aspect of the invention, thefilter housing is divided into two sections. The inlet and outlet portsfor the process stream and the filtered sample port are all located inone section of the housing so that the other section, namely the filtercap, may be removed from the first section without disconnecting anyflow lines from the cap, thus facilitating rapid removal of the cap andreplacement of the filter element therein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of thebypass filter assembly of the present invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 is a sectional view taken along line 33 of FIG. 1;

FIG. 4 is a plan view of the inner face of the filter cap util ized inthe assembly shown in FIG. 1; and

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2 showing thesymmetrical bifurcated flow pattern of fluid in the assembly which isachieved in accordance with the instant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings indetail, the bypass filter assembly of the present invention, generallydesignated 10, comprises a cylindrical housing 12 which is divided intotwo separate sections, namely a filter body 14 and filter cap 16. Thesetwo sections are held together at mating surfaces 18 and 20,respectively, by means of a plurality of bolts 22.

A cylindrical chamber 24 is formed in the body 14 and opens at thesurface 18. The bottom of the chamber 24 provides a flat end wall 26.This wall is generally parallel to the opposite end wall 28 of thechamber which is provided by the inner face of the cap 16. An axiallyextending annular shoulder 30 is formed on the body 14 adjacent itsinner periphery and extends toward the cap 16, but terminates short ofthe end wall 28. A flat circular filter element 34 is positioned betweenthe body 14 and the cap 16. As can be seen, the filter element 34 liesgenerally parallel to the end walls 26 and 28 of the cylindrical chamber24.

Inlet and outlet ports 40 and 42, respectively, are provided in the wallof the filter body 14 to provide communication between the cylindricalinner wall 44 of the chamber 24 and the exterior of the housing. Aninlet line 46 is connected to the port 40 for conveying a process streaminto the chamber 24 while an outlet line 47 is connected into the outletport 42 so as to permit the process stream to exit from the chamber. Ascan be seen in FIG. 2, the outlet port 42 has a greater crosssectionalarea than the inlet port 40 so as to prevent a back pressure from beingbuilt up within the housing 12.

As can best be seen in FIG. 3, the surface 20 on the filter cap 16 isprovided by an annular projection 48 that extends axially outwardly fromthe inner face 28 of the cap. The inner cylindrical surface 49 of thisprojection is spaced radially outwardly from the outer cylindricalsurface 50 of the shoulder 30 on the filter body 14, thereby definingtherebetween an annular space for holding an elastomeric sealing ring52. The thickness of the sealing ring 52 is greater than the length ofthe shoulder 30 on the filter body 14 so that when the filter cap 16 issecured to the body 14 by means of the bolts 22, the sealing ring 52will engage the filter element in sealing relationship and hold itfirmly in place within the housing. In addition, the sealing ring 52assures that there will be no leakage of fluid out of the housing 12between the mating surfaces 18 and 20 of the body and cap, respectively.

According to one feature of the invention, the sample port 54 of thehousing is located in the cylindrical wall of the filter body 14. A line56 is connected to the sample port for delivering filtered sample to aninstrument (not shown) for analysis. The port 54 communicates by meansof a bore 58 to the surface 18 of the filter body 14. The bore 58 is inregistry with a sample passage 60 which extends from the surface 20 onthe cap 16 to the bottom and center of a circular recess 62 formed inthe inner surface 28 of the filter cap. An annular groove 64 surroundsthe sample passage 60 at its opening at the surface 20. An annularsealing ring 66 is located in this groove to provide a seal between themating surfaces 18 and 20 of the filter body 14 and cap 16,respectively, so that there will be no loss of sample fluid passingthrough the passage 60, bore 58 and port 54. With the process streaminlet and outlet lines 46 and 47, respectively, and the sample line 56all connected to the filter body 14, it can be appreciated that thefilter cap 16 may be rapidly removed from the body by removing the bolts22 without uncoupling any lines from the cap. Thus, the filter element34 in the cap 16 may be rapidly and easily replaced, without the timeconsuming and inconvenient requirement of uncoupling any lines from thecap as is required in previous bypass filters.

As will be seen from FIGS. 1 and 5 of the drawings, the bolts 22 arelocated in a nonuniform manner about the periphery of the housing 12 sothat the cap 16 may be mounted onto the filter body 14 in only oneposition. In this position the sample passage 60 in the cap is inregistry with the bore 58 connected to the sample outlet port 54 in thebody 14. This arrangement eliminates the possibility of the filter cap16 being improperly positioned on the body 14.

According to another feature of the invention, the inlet port 40 in thefilter body 14 is directed generally toward the center of thecylindrical chamber 24 so that there will be achieved a generallysymmetrical bifurcated flow of process stream within the chamber asshown by the pattern lines appearing in FIG. 5. Preferably the outletport 42 lies in the same plane as inlet port 40 and is displaced about170 to 180 from the inlet port. The filter element 34 lies in a planewhich is generally parallel to the plane in which the inlet port 40 andoutlet port 42 lie. Thus, a symmetrical bifurcated flow of fluid iscreated adjacent to the filter element. This flow of fluid promotes acounter-rotating scouring or cleaning action on the inner face 68 of thefilter element. This turbulent fiow of the process stream adjacent 'tothe filter element has been found to effectively prevent a build-up ofparticles on the element by'flushing the particles away before they cancause excessive pressure drops across the element, thus greatlyextending the life of the element.

It has been found that when passing a gaseous process stream or liquidhydrocarbon stream through the filter assembly of the present inventionemploying therein a filter element having a pore size of less than 0.8microns, the filter element will effectively prevent the passagetherethrough of free water droplets which exist in the stream. The waterdroplets will collect on the inner surface 68 of the filter element. Theturbulent flow of the process stream within the chamber 24 will carryaway these free water droplets as well as remove a majority ofparticulate matter which becomes entrained on the surface of the filterelement. On the other hand, when the process stream is water, the filterwill remove particulate matter only from the water and will permit thewater to pass therethrough. Thus, the filter assembly of the presentinvention is effective for removing both water particles and particulatematter from gaseous streams and liquid hydrocarbon streams from which asample is desired and also is useful for removing particulate matterfrom water process streams from which there is desired to be drawn aclean liquid water sample for analysis.

In order to establish the effectiveness of the self-cleaning actionachieved by producing a symmetrical bifurcated flow of process stream inaccordance with the present invention, an assembly as described hereinwas connected in parallel with a bypass filter as disclosed in theaforementioned Collins patent to a common source of clean, whitegasoline. identical Millipore MP, 0.5 micron pore size filter elementswere employed in the two assemblies. The gasoline was passed through theassemblies at a flow rate of about 1 gram per minute and the followingmaterials were added to the gasoline at -hour intervals, in sequence:

5 grams Arizona road dust 2 grams talcum powder 2 grams graphite powder3 grams calcium carbonate (chalk) 6 grams soda lime lt'was found that nosignificant change in the pressure drop across either of the filterassemblies occurred as a result of adding the above materials to thegasoline. This establishes that the turbulent flow produced in theassembly of the instant invention is as effective as that produced inthe Collins bypass filter assembly to remove the aforementionedparticulate materials from the filters employed in the assemblies. Inaddition, samples were taken from the sample line of each of the filterassemblies and it was determined by visual examination that the sampleswere equally clean, i.e., free of any particulate material.

Later, 5 grams of Molykote G MOS, paste, a grease-like material, wasadded to thewhite gasoline and passed through the two filter assemblies.Over a period of 75 minutes, the pressure drop across the assembly ofthe instant invention increased from l .7 sig to 11.6 psig while thepressure dro across the Collins ypass filter assembly increased from I.

psig to 17.l psig. The substantial increase in pressure drop across thelatter assembly shows that the filter element therein was essentiallyclogged. Thus, it is concluded that with a grease-like material in theprocess stream, the symmetrical bifurcated flow of process stream'withinthe filter assembly of the instant invention achieves a more effectivecleaning action of the filter element therein than is achieved in theCollins filter assembly in which the process stream enters tangentiallyinto the filter chamber to produce a swirling action.

Thus, by the present invention there is provided an improved bypassfilter assembly which is simple in construction, easy to disassemble toreplace the filter element therein, and does not suffer from a build-upof particulate matter on the filter element for extended periods oftime.

Although only a single embodiment of the invention has been disclosedherein for purposes of illustration, it will be understood that variouschanges can be made in the form, details, arrangement and proportions ofthe various parts in such embodiment without departing from the spiritand scope of the invention as defined by the appended claims.

What is claimed is:

l. A bypass filter assembly for obtaining a filtered sample from aprocess stream or the like comprising:

a housing having a cylindrical chamber therein with generally flat wallsat opposite ends thereof, said walls being generally parallel to eachother;

said housing having inlet and outlet ports therein opening at thecylindrical wall of said chamber adjacent to one of said end walls forpassing a process stream through said chamber;

said ports being disposed generally opposite to each other insubstantially the same plane, said plane lying generally parallel tosaid end walls;

said inlet port being directed generally toward the center of saidchamber;

a generally flat filter lying adjacent and parallel to the other endwall; and

a sample passage in said housing opening at said other end wall andcommunicating with the exterior of said housing.

2. A bypass filter assembly for obtaining a filtered sample from aprocess stream or the like comprising:

a housing having a cylindrical chamber therein;

inlet and outlet ports in said housing opening at the cylindrical wallof said chamber, said ports being disposed generally opposite to eachother in substantially the same plane and said inlet port being directedgenerally toward the center of said cylindrical chamber so that processstream discharging through said inlet port into said chamber will flowin a generally symmetrical bifurcated flow pattern within the chamber;

a filter positioned adjacent to one side of said chamber and disposedgenerally parallel to said plane whereby said process stream will flowin said pattern over one surface of said filter; and

a sample passage in said housing communicating the other surface of saidfilter to the exterior of said housing.

3. A filter assembly as set forth in claim 2 wherein said outlet port islarger than said inlet port.

4. A filter assembly as set forth in claim 2 wherein said inlet andoutlet ports are'displaced from one another approximately to 5. A filterassembly as set forth in claim 2 wherein the pore size of said filter isless than 0.8 microns.

1. A bypass filter assembly for obtaining a filtered sample from aprocess stream or the like comprising: a housing having a cylindricalchamber therein with generally flat walls at opposite ends thereof, saidwalls being generally parallel to each other; said housing having inletand outlet ports therein opening at the cylindrical wall of said chamberadjacent to one of said end walls for passing a process stream throughsaid chamber; said ports being disposed generally opposite to each otherin substantially the same plane, said plane lying generally parallel tosaid end walls; said inlet port being directed generally toward thecenter of said chamber; a generally flat filter lying adjacent andparallel to the other end wall; and a sample passage in said housingopening at said other end wall and communicating with the exterior ofsaid housing.
 2. A bypass filter assembly for obtaining a filteredsample from a process stream or the like comprisinG: a housing having acylindrical chamber therein; inlet and outlet ports in said housingopening at the cylindrical wall of said chamber, said ports beingdisposed generally opposite to each other in substantially the sameplane and said inlet port being directed generally toward the center ofsaid cylindrical chamber so that process stream discharging through saidinlet port into said chamber will flow in a generally symmetricalbifurcated flow pattern within the chamber; a filter positioned adjacentto one side of said chamber and disposed generally parallel to saidplane whereby said process stream will flow in said pattern over onesurface of said filter; and a sample passage in said housingcommunicating the other surface of said filter to the exterior of saidhousing.
 3. A filter assembly as set forth in claim 2 wherein saidoutlet port is larger than said inlet port.
 4. A filter assembly as setforth in claim 2 wherein said inlet and outlet ports are displaced fromone another approximately 170* to 180*.
 5. A filter assembly as setforth in claim 2 wherein the pore size of said filter is less than 0.8microns.